Implement UFCN custom_open_image behaviour in basic open_image function

Closes #65 (closed)

arkindex_worker/models.py

@@ -55,6 +55,14 @@ class Element(MagicDict):
     Describes any kind of element.
     """
 
+    def resize_zone_url(self, size="full"):
+        if size == "full":
+            return self.zone.url
+        else:
+            parts = self.zone.url.split("/")
+            parts[-3] = size
+            return "/".join(parts)
+
     def image_url(self, size="full"):
         """
         When possible, will return the S3 URL for images, so an ML worker can bypass IIIF servers
@@ -79,10 +87,16 @@ class Element(MagicDict):
         bounding_box = polygon_bounding_box(self.zone.polygon)
         return bounding_box.width > max_width or bounding_box.height > max_height
 
-    def open_image(self, *args, max_size=None, **kwargs):
+    def open_image(self, *args, max_size=None, use_full_image=False, **kwargs):
         """
         Open this element's image as a Pillow image.
-        This does not crop the image to the element's polygon.
+
+        If use_full_image is False:
+            Use zone url, instead of the full image url to be able to get
+            single page from double page image.
+        Else:
+            This does not crop the image to the element's polygon.
+
         :param max_size: Subresolution of the image.
         """
         if not self.get("zone"):
@@ -119,7 +133,10 @@ class Element(MagicDict):
             resize = "full"
 
         try:
-            return open_image(self.image_url(resize), *args, **kwargs)
+            if use_full_image:
+                return open_image(self.image_url(resize), *args, **kwargs)
+            else:
+                return open_image(self.resize_zone_url(resize), *args, **kwargs)
         except HTTPError as e:
             if (
                 self.zone.image.get("s3_url") is not None